This invention relates generally to the formation of fastener joints where the thin sheets of material are dimpled and more particularly to a fastener system which automatically dimples the thin sheets of material as an incident to the installation of the fastener in the joint.
Where thin sheets of material are to be fastened together by fasteners, it is common practice to dimple the sheets of material around the holes through which the fastener is installed to enhance the strength of the fastener joint. Usually, the formation of such fastener joints involves drilling pilot holes through the sheets of material where the joint is to be made and then forming a dimple in the sheets around the pilot holes with special tooling. After dimpling, the holes are redrilled to a larger diameter to remove the uneven edges of the sheets of material at the hole formed as an incident to the dimpling operation so that the hole through the sheets of material is smooth with a constant diameter. Finally, the fastener is installed in the thusly formed hole to complete the fastener joint. As is apparent, the number of steps involved in this technique make same relatively expensive to carry out and also increase the incidence of error in connection therewith. Further, the number of fabrication steps involved and the equipment required to carry out this technique make field repair of these dimpled joints difficult and expensive, especially where a new sheet of material is added to the joint.